Precision Instrumentation and Measurement

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Authors: Ling Li Jiang, Yi Lun Liu, Xue Jun Li, Anhua Chen
Abstract: Performing bispectrum analysis on the actual measured vibration signals of the roller bearing with different failure modes, it developed that the spectrum distribution regions are similar among the same failure modes, and distinguishable among the different failure modes, thus this character can be used to classify fault types. The binary images extracted from the bispectra are taken as the feature vectors. The fuzzy clustering analysis based on objective function is applied for pattern recognition, which makes use of the binary image to construct a core and a domain representing the common and scope of bispectrum distribution, respectively, then constructs the objective function as the classify to achieve pattern recognition and diagnosis. The roller bearing fault diagnosis is performed as an example to verify the feasibility of the proposed method.
Authors: Bing Li, Qiao Zhou Nan, Bao Shan Shi, Xue Mei Qin
Abstract: The purpose of this research is to analysis on cell morphology of PC (Polycarbonate) foam in different processing parameters. In this study, foamed PC was produced using a dynamic simulation foaming setup designed by ourselves. Cell morphology was compared as different temperatures, pressures, gas saturation time, pressure drop rates and different shear rates were used. Cell morphology of foamed samples was measured by using scanning electron microscopy(SEM). It was found that foamed samples with better morphology could be obtained as pressure, pressure drop rate and gas saturation time increased.
Authors: Yuan Bao Leng, Shou Gang Zhao, Guang He Zheng
Abstract: Due to various reasons, the inherent quality for Weihe River dike remains poor. There are many hidden defects in dikes, such as cracks, holes etc. so that the actual flood protection ability of dikes is low. And it is difficult to resist the impact of the design flood. In order to ascertain the number, distribution and depth of these hidden defects, etc., electrical detecting technique was applied and studied for detection of hidden defects. At the same time, in order to verify the correctness of the detection results of hidden defects, the engineering geological survey for the purpose of verification was carried out on the detection dike sections. Survey results confirmed the reliability of detection conclusions.
Authors: Shou Gang Zhao, Jun Xia Zhang, Rui She Qiao
Abstract: In order to supervise the safe operation of the Changma dam, to test design, to validate construction quality and run behavior, to monitor accidents as well as the accumulation of information on evaluation of the dam's future behavior and so on, the deformation and stress-strain of reservoir dam are carried out safety monitoring. Monitoring results show that the development of settlement deformation is still increasing, and have not yet reached a relatively stability according to the development trend of the settlement process. Lateral deformation of the dam isn’t abnormal phenomenon, and accords with the general laws of dam deformation. The compressive stress of dam increases with the increase of the overlay soil layer thickness, the vertical stress is bigger than horizontal or diagonal stress, the measured value and the change process are in line with general law. At present, Changma dam is safe and stable operation.
Authors: Tin Gyi Zhang, Yuan Bao Leng, Dan Ying Gao
Abstract: Based on the principle of electrical measurement method, the clip gauge was made to measure the crack opening displacement (COD).Through the three-point bending test on the specimens of steel fiber reinforced high strength concrete (SFHSC), the effect of the fiber volume fraction (ρf) upon the critical crack opening displacement (the critical crack tip opening displacement and the critical crack mouth opening displacement) was studied. The result shows that the effect of ρf on mouth-tip ratio (the ratio of critical crack mouth opening displacement to critical crack tip opening displacement) can reflect its effect upon the critical crack opening displacement. According to the geometrical relationship between the initial crack length and the critical crack opening displacement,calculation method for the initial crack length was proposed. Based on the test result, the formula was established for calculating the critical crack tip opening displacement.
Authors: Rui Wang, Yuan Bao Leng, Chang Zheng Li
Abstract: Sub-bottom profiler is a kind of underwater acoustic imaging equipment. It can scan the sub-water stratums with acoustic signals and presents the section imaging. The frequency rang and transmitting power are key points to choice a suitable profiler. Generally, high frequency means high resolution and small imaging range. Transmitting power affects the imaging range also. Sub-bottom profiler can tell hydraulic and civil engineers what the embankments’ foundation like, especially the distribution of enrockments. With these information, engineers can evaluate the safety of embankments and decide what to do to keep them standing strong. A typical profiler called X-Star and a series of experiments carried on Yellow River, the famous sediment-laden and the 2nd longest river of China.
Authors: Yan Lan, Jun Xia Zhang, Min Zhang, Shou Gang Zhao
Abstract: The soil unsaturated property is one of the main factors happening dike dangers such as craze and hole, even seriously slope collapse in the Yellow River dike. Based on the study of unsaturated mechanical experiment, the soil shear strength model formula can be proposed , and the changing rule of unsaturated soil mechanical properties be investigated for the typical levee soil of the Yellow River. It can provide theoretical and technical support for preventing the dike danger occurring, reducing the danger rate during the flood season, and establishing defend methods and instructing flood-defended.
Authors: Xian Feng He, Shou Gang Zhao, Yuan Bao Leng
Abstract: The corrosion of steel will have a bad impact on the safety of reinforced concrete structure. In severe cases, it may even be disastrous. In order to understand the impact of steel corrosion on the structure, tests are carried out to study corrosion and expansion rules of steel bars as well as the impact rules of corrosion on bond force between steel and concrete. The results show that wet and salty environment will result in steel corrosion; relatively minor corrosion will not cause expansion cracks of protection layers; when steel rust to a certain extent, it will cause cracks along the protection layer; when there exists minor corrosion in steel and the protection layer does not have expansion cracks, the bond force is still large and rapidly decreases as the corrosion rate increases.
Authors: Xian Feng He, Yuan Bao Leng, Shou Gang Zhao
Abstract: Affected by both of the internal and external factors during work process, the dam monitoring effect variable often generates complex cycles such as jumps, compendium, and re-jumps, which shows a high degree of non-linearity that brings a lot of trouble in the establishment of regular dam safety monitoring forecast model. Drawing on the threshold thought of the threshold autoregressive model, the threshold factor and the threshold value are introduced in the conventional regression model. By making use of the suggested best fitting correlation analysis method to determine the threshold factor and the threshold value, the threshold regression model is established. Application example shows that the method for dam safety monitoring forecast can obtain satisfactory results.
Authors: Qing Ming Zhang, Ping Yu Zhu, Shao Li Wang, Yuan Bao Leng
Abstract: Based on briefly introducing the works of BOTDR, article studied on dike strain monitoring by using the distributed optical fiber measurement system produced by OMNISENS in Swiss. Builded the dike model, monitored the dike strain changes influenced by seepage and loading, we try to verify the feasibility that the distributed optical fiber measurement system can basically reflect the dike deformation. It can be an important direction for the development of dike strain monitoring.

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